On the day before President Trump fired FBI Director James B. Comey, he summoned his vice president, chief of staff, top lawyer and other senior advisers to the Oval Office.

He was ready to get rid of Comey, Trump told them that Monday morning in May, and had prepared a termination letter that laid out in detail his many frustrations, which had boiled over the previous weekend at his private golf club in Bedminster, N.J.

The multi-page letter blasted Comey over his investigation of Trump's Democratic presidential opponent, Hillary Clinton. And, according to a person with direct knowledge of the contents of the letter, it conveyed Trump's displeasure that Comey would not say publicly what he had told the president three times privately: that the FBI's probe into Russia's interference in the 2016 election was not focused on him.

Trump ended up shelving that letter in favor of a far shorter one, but the draft has taken on new significance in the probe by special counsel Robert S. Mueller III, who is examining it as he determines whether Trump's firing of Comey was part of an effort to obstruct justice, according to people with knowledge of the investigation.

The draft, which was first reported by the New York Times, establishes Trump's thinking prior to the firing and contradicts initial statements from White House officials about why he dismissed his FBI director.

In the termination letter Trump sent to Comey, the president described his decision as having been prompted by recommendations from Comey's supervisors — Attorney General Jeff Sessions and Deputy Attorney General Rod J. Rosenstein — a rationale embraced at first in public statements by White House officials, including Vice President Pence.

But the draft letter, which was prepared with the help of senior policy adviser Stephen Miller and described by people familiar with it as a "rant," makes clear what the White House eventually acknowledged: that Trump had essentially decided to fire Comey before he solicited recommendations from Sessions and Rosenstein.

Though the letter is largely about other issues, it could shed light on Trump's state of mind regarding Comey at the time the FBI chief was leading the Russia inquiry that was emerging as a threat to Trump's presidency.

Furthermore, the Oval Office discussion suggests that Pence and other top aides who echoed the initial public explanation for Comey's ouster did not provide a full accounting of Trump's decision process.

Mueller is likely to look into whether Trump, in consulting the Justice Department's top two officials, was seeking a pretense to fire his FBI director or, as some White House advisers said Friday, whether he was simply persuaded to consider their opinions before acting.

This account of Comey's firing, including details about the letter, was provided by several people familiar with the events.

"I can't comment on anything the special counsel might be interested in," White House attorney Ty Cobb said. "But this White House is committed to being open and transparent with the special counsel's investigation."

A Mueller spokesman declined to comment.

At the Oval Office meeting on Monday, May 8, Trump described his draft termination letter to top aides who wandered in and out of the room, including then-Chief of Staff Reince Priebus, White House Counsel Donald McGahn and senior adviser Hope Hicks. Pence arrived late, after the meeting had begun. They were also joined by Miller and Trump's son-in-law, Jared Kushner, both of whom had been with Trump over the weekend in Bedminster. Kushner supported the president's decision.

The letter had been drawn up by Miller, acting as a stenographer to capture Trump's thoughts, according to several people with knowledge of the process. While it did not dwell on Russia, the draft included language similar to what was included in the final version ultimately sent by Trump: "While I greatly appreciate you informing me, on three separate occasions, that I am not under investigation, I nevertheless concur with the judgment of the Department of Justice that you are not able to effectively lead the Bureau."

After hearing about Trump's decision and the contents of the letter, some of the president's aides were shocked and chagrined. They urged caution.

At one point, Trump was warned that firing Comey would not end the Russia investigation but would instead probably extend it. He acknowledged the likelihood but said he believed firing Comey was the right move and wanted to push ahead.

McGahn raised another point: Sessions and Rosenstein were scheduled to visit the White House later the same day, and they had also been expressing displeasure with the FBI director. Shouldn't Trump consult the two Justice officials, who were Comey's supervisors, before moving forward?

Trump agreed, meeting with Sessions and Rosenstein later that day. The president gave them a copy of his draft letter to explain his thinking, according to people familiar with the discussions.

The next day, Sessions submitted to the White House a brief letter outlining his position: He wrote that he had concluded a "fresh start" was needed at the FBI. Rosenstein provided a longer memo, in which he outlined missteps he believed Comey had made in the course of the Clinton email probe, including criticizing Clinton's conduct publicly despite announcing that she would face no criminal charges. Rosenstein called Comey's derogatory comments a "textbook example of what federal prosecutors and agents are taught not to do."

Shortly afterward, Trump dispatched his longtime security chief, Keith Schiller, to the Justice Department to hand-deliver his letter formally firing the FBI chief. Attaching the letters from Sessions and Rosenstein, Trump wrote, "I have accepted their recommendation and you are hereby terminated and removed from office, effective immediately."

The newly described sequence of events could help the White House bolster its argument that Trump had soured on Comey and wanted him out — and that his decision was not intended to disrupt the Russia probe.

Mueller will weigh the narrative with other events that led up to Comey's firing, including Comey's account of Trump's efforts to intercede by requesting that the FBI director drop an investigation of former national security adviser Michael Flynn.

But the incidents leading up to Comey's removal also raise questions about how the White House initially explained the firing to the public.

In a hastily called media availability on the night of the firing, then-press secretary Sean Spicer told reporters that the Russia investigation had played no role in the dismissal, which he said had been led by the Department of Justice. "No one from the White House," Spicer said, when asked who drove the decision. "That was a DOJ decision."

Spicer had not been at the Oval Office meeting where Trump's draft letter was discussed and the communications team had been told of the firing — along with the purported justification for it — only moments before it became public. Spicer declined to comment for this report.

Pence, who had been in the Oval Office for part of the meeting, told reporters during a visit to Capitol Hill on Wednesday, May 10, that Trump had acted at Sessions's and Rosenstein's recommendation. "Let me be clear with you, that was not what this is about," Pence said when asked whether Trump fired Comey to impede the Russia investigation.

Pence's lawyer Richard Cullen said the vice president "stands by his statement."

"It was true then, and it is true today," he said.

The events leading to Comey's firing also raise questions for Rosenstein, who now holds authority over the special counsel's investigation because Sessions recused himself over his role as a Trump campaign adviser.

Rosenstein had been provided Trump's letter prior to submitting his own memo about Comey's conduct.

Rosenstein has previously confirmed that he learned while meeting with Trump on May 8 that the president intended to remove Comey from his post.

"Notwithstanding my personal affection for Director Comey, I thought it was appropriate to seek a new leader," Rosenstein said in a statement to Congress.

He said he finalized his memo the next day, asking an ethics expert who had worked in the deputy attorney general's office during multiple administrations to review it first. He said he told that attorney that Trump was going to remove Comey and that he was "writing a memorandum to the Attorney General summarizing my own concerns."

"I wrote it. I believe it. I stand by it," Rosenstein said in a statement to Congress.

Rosenstein told the Associated Press in June that he was open to recusing himself from his position of authority over the Mueller probe, if that became necessary because his own actions were part of the investigation.

"I've talked with Director Mueller about this," Rosenstein told the AP. "He's going to make the appropriate decisions, and if anything that I did winds up being relevant to his investigation, then, as Director Mueller and I discussed, if there's a need from me to recuse, I will."

Ian Prior, a Justice Department spokesman, said, "The Department of Justice does not comment on communications with the White House."